As a conventional technology of a saw chain sharpener, an upper blade grinding equipment for a chainsaw, for example, described in Japanese Laid-open Utility Model Publication Sho 61-24121 can be mentioned. This grinding equipment has: a holder 9 formed of a small motor; a rod-shaped grindstone 11 which is attached to a chuck 10 at an end of the holder 9 and can be rotated by a motor; a ring member 14 attached to an attachment member 12 at an end portion of the holder 9; a holding body 13 having a cover plate 16 extending from the ring member 14 in parallel with the grindstone 11 at both ends of the grindstone 11; and a grindstone retainer 19 having a retaining rod 20 which is fixed to an end portion of the cover plate of the holding body 13 by a fixing member 15, and which is opposed to the grindstone 11 and fixed at a free position on the same center axis as the grindstone.
This upper blade grinding equipment for a chainsaw is used in a procedure: that the holder 9 is held by a hand; that the rod-shaped grindstone 11 is rotated by the motor drive so as to bring the cover plate 16 of the holding body 13 into contact on a chain body 1; that a retaining rod 8 and the retaining rod 20 is brought into contact with an upper blade and upper blade 8 of a cutter blade link 2 so as to define a sharpening angle; and that thereafter a front end of the upper blade and the upper blade 8 are sharpened by being ground with the rotating rod-shaped grindstone 11 at a position where the entire equipment is shifted forward along the sharpening angle.
As another conventional technology, a saw chain sharpener described in Japanese Laid-open Utility Model Publication Sho 57-186227 can be mentioned, which does not need a grinding tool. This sharpener is constructed in a manner: that a cylinder-shaped grindstone 3 is attached to an end portion of a drive shaft of a motor 2; that attached to a lower front part of the motor 2 is an angle adjustment plate 1 which has a substantial pentagon-shape as seen in plan view, two sides of which at a front end are bent vertically downward to form front plate portions; and that a depth adjustment plate 6 is pivotally supported by a front end of each front plate portion of the angle adjustment plate 1 so as to be adjustable in an up-down direction.
This sharpener is used in a procedure: that the grindstone 3 is rotated by the motor; that either of the front surfaces of the angle adjustment plate 1 is brought into contact along a side portion of the saw chain so as to align the orientation of the grindstone 3 with a sharpening angle of an upper blade; and that a lower surface of the depth adjustment plate 6 is brought into contact with an upper end of the saw chain, and the height of the depth adjustment plate 6 is adjusted so as to set the grindstone 3 at an optimum height, whereby the sharpening is done the grindstone 3.
However, when using the above described grinding equipment or the sharpener, a hand is used to hold the holder or the motor 2 so as to place the cover plate 16 or the angle adjustment plate 1 on the saw chain. This has caused a problem that although the holding of the holder or the motor 2 by hand is likely to cause instability in itself, there is no support, and that the mere placing of the cover plate 16 or the angle adjustment plate 1 on the saw chain is insufficient to stabilize the posture of the grinding equipment or the sharpener.
Thus, conventionally, there has been a problem that it is difficult to do an accurate sharpening or sharpening which is aligned with a sharpening angle, so that the hand gets tired, and the work efficiency gradually decreases.